Colorectal cancer (CRC) is the second leading cause of cancer in Puerto Rico (PR) accounting for approximately 1,500 individuals annually, which represent 12% of all cancer cases in the island. The genetic epidemiology of CRC among Hispanic populations is not well studied, hence studies focused on large, well defined ethnic groups such as Puerto Ricans, are clearly warranted. The first step towards evaluating the molecular, environmental, and genetic epidemiology of CRC in PR is to establish a population-based familial CRC registry. The following specific aims have been proposed: Specific Aim 1: To prospectively identify and recruit approximately 300 CRC probands from two distinct geographical areas in PR (Metropolitan and Southern Region). From each proband we will obtain a pedigree extended to second-degree relatives and cousins. Assuming 10% will be positive for a family history of CRC, we will then recruit all 30 probands with a family history of CRC and a sample of 15 family-history negative probands and obtain: paraffin-embedded tumors blocks, blood samples, risk factor and food frequency questionnaires. Specific Aim 2: To prospectively identify and recruit selected relatives (parents, grandparents, and same generation relatives - cousins and siblings) from the 45 probands identified in Specific Aim 1. In addition, for siblings and cousins of probands (i.e. relatives in the same generation as the proband), we will obtain risk factor and food frequency questionnaires, and for colorectal cancer cases, tumor blocks and pathology reports of their cancers. Specific Aim 3: To estimate from this pilot study the following parameters: (a) response rate of probands and their selected relatives;(b) response rate of participants for each data item;(c) family history of CRC and other cancers;(d) number of living first- and second-degree relatives and cousins of probands;(e) number of these relatives who live in the same household and region/municipality;(f) prevalence/distribution of selected risk factors from the administered questionnaires. During this two-year pilot study we propose to determine the feasibility for implementation of a population- based familial CRC registry in PR. Our long-term objective is to conduct a large, island-wide, population- based, genetic-epidemiologic study of familial CRC in PR. Data obtained from this two-year pilot study will serve as the foundation for our large, island-wide, population-based, genetic-epidemiologic study of familial CRC in Puerto Rico.